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Determinants Introduction         Each n -square matrix A = [a ij ] is assigned a special scalar called the determinant of A , denoted by det ( A )  or | A | or                          An n ✕ n   array of scalars enclosed by straight lines, called a  determinant of order n, is not a matrix but denotes the determinant of the enclosed array of scalars, i.e., the enclosed matrix.           The determinant function was first discovered during the investigation of systems of linear equations. The determinant is an indispensable tool in investigating and obtaining properties of square matrices.   Determinants of Order 1 and 2 The Determinants of Order 1 and 2 are defined as follows: The determinant of a 1x1  matrix  A = [a 11 ]  is the scalar  a 11  itself, that is,     ...

Calculation of a 3x3 matrix determinant using Triangle's Rule. The Triangle’s rule will be formed with this scheme:                                                 The product of diagonal elements and product of elements in the both vertex of two triangles of the first determinant get the “+” sign and the product of diagonal elements and product of elements in the both vertex of two triangles of the second determinant get the “-” sign. In base of triangle’s rule, we have: This method is somehow similar to  Sarrus Rule .

Calculation of 3 ✖ 3 matrix determinant by  Co-factor Expansion along the Column The Co-Factor Expansion Definition : If  A   is a square matrix then the minor of  A ij , denoted by  M ij , which is the determinant of the sub-matrix that results from removing (deleting) the row  ith   and  jth  column of   A . Sign Chart for a 3×3 determinant                                                      A sign chart is either a + or - for each element in the matrix. The first element (row 1, column 1) is always a + and it alternates from there. Note:  The + does not mean positive and the - negative. The + means the same sign as the minor and the - means the opposite of the minor. Think of it as addition and subtraction rather than positive or ne...

Calculation of 3x3 matrix determinant by  Row Echelon Form About the method ( Gaussian Elimination ) To calculate a determinant you need to do the following steps: Set the matrix (must be square) Reduce this matrix to row echelon form using elementary row operations so that all the elements below the diagonal are zero. Multiply the main diagonal elements of the matrix - determinant is calculated.

Calculation of 3 ✖ 3 matrix determinant by Co-factor Expansion along the Row The Co-Factor Expansion Definition : If A   is a square matrix then the minor of A ij , denoted by M ij , which is the determinant of the sub-matrix that results from removing (deleting) the row ith   and jth  column of  A . Sign Chart for a 3×3 determinant                                                                  A sign chart is either a + or - for each element in the matrix. The first element (row 1, column 1) is always a + and it alternates from there. Note: The + does not mean positive and the - negative. The + means the same sign as the minor and the - means the opposite of the minor. Think of it as addition and subtraction rather than positive or negative. About the Method To calc...

Calculation of  a 3x3 matrix  determinant  using Sarrus Rule .